Synthesis of Biologically Active Amines via Rhodium−Bisphosphite-Catalyzed Hydroaminomethylation

Selective and stable tetraphosphite for Rh-catalyzed linear hydroaminomethylation of aliphatic and aromatic terminal olefins

A highly selective and stable tetraphosphite ligand TBTP was reported for Rh-catalyzed linear selective hydroaminomethylation of both aliphatic and aromatic terminal olefins, giving up to 10 000 TON, 99.9% linear amines with isolated yields up to 98.2%.

Synthesis of Mannich-type derivatives from amides activated by hydrogen bonding with ZnCl2

The amide group has one of the most significant functionalities found in many natural products. Herein, low-nucleophilic amides are used in a Mannich-type reaction to synthesize N-acyl-protected amine derivatives. A highly efficient synthetic method utilizing simple aldehydes, N-substituted anilines, and amides as substrates was established through a one-pot amide pathway activated by hydrogen bonding between the ZnCl₂ and amide under solvent-free conditions. This strategy can be broadly applied to medicinal chemistry. More importantly, compared with the previous Lewis acid catalyzed reaction, we proposed a new application of zinc chloride.

Dithienopyrrole Derivatives with Nitronyl Nitroxide Radicals and Their Oxidation to Cationic High-Spin Molecules

Three 1 N‐phenyl nitronyl nitroxide (NN) 4‐substituted dithieno[3,2‐b:2′,3′‐d]pyrrole (DTP) derivatives with R1=4‐phenyl‐, 4H‐, and 4‐methylthiothiophenyl‐ (R¹₂DTP‐Ph‐NN, R¹=H, Ph and MeSTh) were designed, synthesized and characterized. The electrochemical properties were studied by cyclic voltammetry (CV). All the molecules exhibited two main oxidation peaks, first for radical cation and next for dication formation. The cation and dication formation were also confirmed by UV/Vis absorption spectroscopy for Ph₂DTP‐Ph‐NN and MeSTh₂DTP‐Ph‐NN titrated with tris(4‐bromophenyl)aminiumhexachloroantimonate (magic blue). In addition, the cation and dication formation were verified by EPR spectroscopy. Finally, the exchange interactions (J/k_B) of NN and radical cation were calculated by DFT studies.

Efficient synthesis of chiral γ-aminobutyric esters via direct rhodium-catalysed enantioselective hydroaminomethylation of acrylates

The first successful rhodium catalysed asymmetric hydroaminomethylation of alkenes using a single catalyst is reported with ees up to 86%.

A Multicatalytic Approach to the Hydroaminomethylation of α-Olefins

We report an approach to conducting the hydroaminomethylation of diverse α-olefins with a wide range of alkyl, aryl, and heteroarylamines at relatively low temperatures (70-80 °C) and pressures (1.0-3.4 bar) of synthesis gas. This approach is based on simultaneously using two distinct catalysts that are mutually compatible. The hydroformylation step is catalyzed by a rhodium diphosphine complex, and the reductive amination step, which is conducted as a transfer hydrogenation with aqueous, buffered sodium formate as the reducing agent, is catalyzed by a cyclometallated iridium complex. By adjusting the ratio of CO to H₂ , we conducted the reaction at one atmosphere of gas with little change in yield. A diverse array of olefins and amines, including hetreroarylamines that do not react under more conventional conditions with a single catalyst, underwent hydroaminomethylation with this new system, and the pharmaceutical ibutilide was prepared in higher yield and under milder conditions than with a single catalyst.

Discovery and Rational Design of Natural-Product-Derived 2-Phenyl-3,4-dihydro-2H-benzo[f]chromen-3-amine Analogs as Novel and Potent Dipeptidyl Peptidase 4 (DPP-4) Inhibitors for the Treatment of Type 2 Diabetes

Starting from the lead isodaphnetin, a natural product inhibitor of DPP-4 discovered through a target fishing docking based approach, a series of novel 2-phenyl-3,4-dihydro-2H-benzo[f]chromen-3-amine derivatives as potent DPP-4 inhibitors are rationally designed utilizing highly efficient 3D molecular similarity based scaffold hopping as well as electrostatic complementary methods. Those ingenious drug design strategies bring us approximate 7400-fold boost in potency. Compounds 22a and 24a are the most potent ones (IC50 ≈ 2.0 nM) with good pharmacokinetic profiles. Compound 22a demonstrated stable pharmacological effect. A 3 mg/kg oral dose provided >80% inhibition of DPP-4 activity within 24 h, which is comparable to the performance of the long-acting control omarigliptin. Moreover, the efficacy of 22a in improving the glucose tolerance is also comparable with omarigliptin. In this study, not only promising DPP-4 inhibitors as long acting antidiabetic that are clinically on demand are identified, but the target fish docking and medicinal chemistry strategies were successfully implemented.

Diene hydroaminomethylation via ruthenium-catalyzed C-C bond forming transfer hydrogenation: beyond carbonylation

Under the conditions of ruthenium catalyzed transfer hydrogenation using 2-propanol as terminal reductant, 1,3-dienes engage in reductive C-C coupling with formaldimines obtained in situ from 1,3,5-tris(aryl)-hexahydro-1,3,5-triazines to form homoallylic amines. Deuterium labelling studies corroborate a mechanism involving reversible diene hydroruthenation to form an allylruthenium complex that engages in turn-over limiting imine addition. Protonolysis of the resulting amidoruthenium species releases product and delivers a ruthenium alkoxide, which upon β-hydride elimination closes the catalytic cycle. These transformations, which include enantioselective variants, represent the first examples of diene hydroaminomethylation.

Recent progress in rhodium-catalyzed hydroaminomethylation

This review covers the recent studies featuring the development of catalysts for alkene hydroaminomethylation.

Selenium as a versatile center in fluorescence probe for the redox cycle between HClO oxidative stress and H2S repair

Selenium is a biologically important trace element and acts as an active center of glutathione peroxidase (GPx). GPx is the important antioxidant enzyme to protect organisms from oxidative damage via catalyzing the reaction between ROS and glutathione (GSH). Mimicking the oxidation-reduction cycles of the versatile selenium core in GPx, we can develop fluorescence probes to detect oxidation and reduction events in living systems. The cellular redox balance between hypochloric acid (HClO) and hydrogen sulfide (H2S) has broad implications in human health and diseases, such as Alzheimer's disease (AD). Therefore, to further investigate the roles of this redox balance and understand the pathogenesis of neurodegenerative diseases, it is necessary to detect the redox state between HClO and H2S in real time. We have developed a reversible fluorescence probe MPhSe-BOD for imaging of the redox cycle between HClO and H2S based on oxidation and reduction of selenide in living cells.

Recent advances in catalytic C-N bond formation: a comparison of cascade hydroaminomethylation and reductive amination reactions with the corresponding hydroamidomethylation and reductive amidation reactions

The design and catalytic implementation of tandem reactions to selectively create nitrogen-containing products under mild conditions has encountered numerous challenges in synthetic chemistry. Several known classes of homogeneously catalyzed carbon-nitrogen bond formation including hydroamination, hydroamidation, hydroaminoalkylation, hydroaminomethylation and reductive amination were reported in the literature. More recently, a new class of C-N bond formation consisting of hydroamidomethylation and reductive amidation extended the applicability of these synthetic methodologies. The tandem reactions do considerably impact on the selectivity and efficiency of synthetic strategies. This review highlights and compares selected examples of the hydroaminomethylation, reductive amination, hydroamidomethylation and reductive amidation reactions, and thus consequently reveals their potential applications in synthetic chemistry as well as chemical industries.

Rhodium-catalyzed hydroaminomethylation of cyclopentadiene

The substance class of amines is highly relevant for chemical and pharmaceutical industries. A one-step rhodium catalyzed direct route from cyclopentadiene to saturated C₆-amines is presented via hydroaminomethylation.

Rhodium-catalyzed regioselective hydroaminomethylation of terminal olefins with pyrrole-based tetraphosphorus ligands

A protocol was developed to prepare linear amines by regioselective hydroaminomethylation of terminal olefins with pyrrole-based tetraphosphorus ligands. The reactivity of the ligand is modulated by the substituent of the biphenylphosphane moiety, with ligand L5 exhibiting the highest reactivity.

Chemo- and regioselective homogeneous rhodium-catalyzed hydroamidomethylation of terminal alkenes to N-alkylamides

A rhodium/xantphos homogeneous catalyst system has been developed for direct chemo- and regioselective mono-N-alkylation of primary amides with 1-alkenes and syngas through catalytic hydroamidomethylation with 1-pentene and acetamide as model substrates. For appropriate catalyst performance, it appears to be essential that catalytic amounts of a strong acid promoter, such as p-toluenesulfonic acid (HOTs), as well as larger amounts of a weakly acidic protic promoter, particularly hexafluoroisopropyl alcohol (HOR(F) ) are applied. Apart from the product N-1-hexylacetamide, the isomeric unsaturated intermediates, hexanol and higher mass byproducts, as well as the corresponding isomeric branched products, can be formed. Under optimized conditions, almost full alkene conversion can be achieved with more than 80% selectivity to the product N-1-hexylamide. Interestingly, in the presence of a relatively high concentration of HOR(F) , the same catalyst system shows a remarkably high selectivity for the formation of hexanol from 1-pentene with syngas, thus presenting a unique example of a selective rhodium-catalyzed hydroformylation-hydrogenation tandem reaction under mild conditions. Time-dependent product formation during hydroamidomethylation batch experiments provides evidence for aldehyde and unsaturated intermediates; this clearly indicates the three-step hydroformylation/condensation/hydrogenation reaction sequence that takes place in hydroamidomethylation. One likely role of the weakly acidic protic promoter, HOR(F) , in combination with the strong acid HOTs, is to establish a dual-functionality rhodium catalyst system comprised of a neutral rhodium(I) hydroformylation catalyst species and a cationic rhodium(III) complex capable of selectively reducing the imide and/or ene-amide intermediates that are in a dynamic, acid-catalyzed condensation equilibrium with the aldehyde and amide in a syngas environment.

Real-time mechanistic monitoring of an acetal hydrolysis using ultrafast 2D NMR

Ultrafast (UF) 2D NMR makes it possible to obtain a 2D NMR spectrum in less than a second. Here, UF-HSQC experiments are used for the real-time mechanistic study of an acetal hydrolysis at ¹³C natural abundance, and it is possible to characterize the presence of the hemiacetal, an intermediate with a well-known short lifetime. The assignments are confirmed and rationalized by quantum calculations of ¹H and ¹³C NMR chemical shifts and natural bonding orbital analysis.

Mild Pd-catalyzed N-arylation of methanesulfonamide and related nucleophiles: avoiding potentially genotoxic reagents and byproducts

A convenient, general, and high yielding Pd-catalyzed cross-coupling of methanesulfonamide with aryl bromides and chlorides is reported. The use of this method eliminates concern over genotoxic impurities that can arise when an aniline is reacted with methanesulfonyl chloride. The application of this method to the synthesis of dofetilide is also reported.